1 /* @(#)s_modf.c 5.1 93/09/24 */ 2 /* 3 * ==================================================== 4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5 * 6 * Developed at SunPro, a Sun Microsystems, Inc. business. 7 * Permission to use, copy, modify, and distribute this 8 * software is freely granted, provided that this notice 9 * is preserved. 10 * ==================================================== 11 */ 12 13 #include <sys/cdefs.h> 14 #if defined(LIBM_SCCS) && !defined(lint) 15 __RCSID("$NetBSD: s_modf.c,v 1.11 2002/05/26 22:01:57 wiz Exp $"); 16 #endif 17 18 /* 19 * modf(double x, double *iptr) 20 * return fraction part of x, and return x's integral part in *iptr. 21 * Method: 22 * Bit twiddling. 23 * 24 * Exception: 25 * No exception. 26 */ 27 28 #include "math.h" 29 #include "math_private.h" 30 31 static const double one = 1.0; 32 33 double 34 modf(double x, double *iptr) 35 { 36 int32_t i0,i1,j0; 37 u_int32_t i; 38 EXTRACT_WORDS(i0,i1,x); 39 j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ 40 if(j0<20) { /* integer part in high x */ 41 if(j0<0) { /* |x|<1 */ 42 INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */ 43 return x; 44 } else { 45 i = (0x000fffff)>>j0; 46 if(((i0&i)|i1)==0) { /* x is integral */ 47 u_int32_t high; 48 *iptr = x; 49 GET_HIGH_WORD(high,x); 50 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 51 return x; 52 } else { 53 INSERT_WORDS(*iptr,i0&(~i),0); 54 return x - *iptr; 55 } 56 } 57 } else if (j0>51) { /* no fraction part */ 58 u_int32_t high; 59 *iptr = x*one; 60 GET_HIGH_WORD(high,x); 61 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 62 return x; 63 } else { /* fraction part in low x */ 64 i = ((u_int32_t)(0xffffffff))>>(j0-20); 65 if((i1&i)==0) { /* x is integral */ 66 u_int32_t high; 67 *iptr = x; 68 GET_HIGH_WORD(high,x); 69 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 70 return x; 71 } else { 72 INSERT_WORDS(*iptr,i0,i1&(~i)); 73 return x - *iptr; 74 } 75 } 76 } 77